Learning to identify moths – part 1

Feeling a little overwhelmed by all the moths fluttering to your lights at night? It can seem a bit daunting at first. With upwards of 1000 species or more potentially being recorded in any given area (with higher numbers in the south or in habitat rich regions), your reservations are justified. Even the best birder, who can identify every single species of bird in North America, still only has some 700-odd species to contend with.

Still, there is some measure of satisfaction in being able to identify something, whether it be bird or moth or tree. There are a few species in any group that are easy to identify simply based on colour or pattern. Among North American birds, for example, nothing quite looks like a robin, with its gray back and orange-red belly. The same is true of moths, of course. Everybody knows the soft pale green of the Luna Moth, often seen floating through the room in sleep-aid medication commercials.

But it’s not just the smooth green that helps us identify the moth as a Luna. The other two characteristics we key in on are its size (quite large) and the two long tails streaming from its hindwings. Just like as with birds, size and shape are the most important characteristics to note when trying to identify a moth. Different groups of moths have different characteristics that set them apart. Once you’ve narrowed your moth down to a particular family or group, it’s much easier to then use the colours or pattern to make an identification.

There are two large, distinct groups of moths. The micromoths are 90% little wee guys (there are a couple of larger species that are classified in with them), and taxonomically make up the first half of a field guide. The macromoths are typically larger, and taxonomically come later in lists. It’s usually macromoths that are treated in most field guides. For instance, Covell, in the ex-Peterson guide, has just three and a half of 64 plates given over to micros. Most micros tend to be harder to identify than the macros, simply because their size makes it harder to pick out distinctive field marks.

However, one rarely chooses begin with the tough groups when learning to identify something new. Who starts with sparrows or warblers? Usually you begin with learning to identify the robin, Blue Jay, chickadee. The easy stuff. So let’s begin with the easy stuff. Here are some of the groups that I found the easiest to identify (at least to group) when I was starting out. By being able to recognize some common and characteristic groups, it makes it easier to quickly figure out where in the field guide you should be looking for the ID.

Groups ending in -idae represent the taxonomic level of family, while those ending in -inae are subfamilies.

Sphingidae – the sphinx moths
The sphinxes are characterized by tapered, chunky abdomens and long, narrow wings. A few of these are daytime feeders, and when they’re hovering in front of a flower in a garden can often be confused for a small hummingbird. The ones with slightly less pointy wings often have eyespots on their hindwings, while the ones with pointy wings usually don’t.

Noctuidae – Catacolinae – the underwings
These are mostly (though not all) large moths, with brightly-coloured hindwings. A few have dark hindwings, but all moths in this group share the characteristic broad wings that form a thick triangle when folded.

Pterophoridae – the plume moths
These are one of the most distinctive of families. Sometimes colloquially called the airplane moths, they have skinny little abdomens and long, narrow wings. They’re not very big, less than an inch and sometimes only half an inch in length.

Arctiidae – Arctiinae – the tiger moths
Arctiidae is a broad family that includes moths with a number of different appearances. However, the quintessential “tiger moth”, primarily those in the taxonomic tribe Arctiini, has a fuzzy thorax, a lightly furry abdomen (commonly orange or pink), longish triangular wings, and is often (though not always) brightly coloured. There are a couple other groups that are also fuzzy, but they tend to either be more stocky, all-over fuzzy, have broader wings, or fuzzy legs.

Noctuidae – Plusiinae – the loopers
Superficially similar in shape to the tiger moths, the loopers tend to have a more strongly “tented” appearance, with wings that are broader at the outside tip than those of tiger moths. Loopers also usually have a hunch-backed appearance as their furry thorax forms shapely little tufts that make their head seem quite low. Many have a loopy little spot in the middle of their wing, as per the last photo.

Thank you so much for your help. I am putting together a collage of moths to donate to my friends private school, and am having a hard time identifying all of them. I have collected 36, and have only identified 4!

It takes a while to get proficient at identification, Amy – I’ve been at it more than four years, and I still struggle at times! Keep at it, it will get easier. The new Peterson Field Guide to Moths will be released on April 17 – you could get your hands on a copy of that, and it will probably help. Good luck!